update pdf document loaders' metadata source to url for online pdf (#13274)

- **Description:** Update 5 pdf document loaders in
`langchain.document_loaders.pdf`, to store a url in the metadata
(instead of a temporary, local file path) if the user provides a web
path to a pdf: `PyPDFium2Loader`, `PDFMinerLoader`,
`PDFMinerPDFasHTMLLoader`, `PyMuPDFLoader`, and `PDFPlumberLoader` were
updated.
- The updates follow the approach used to update `PyPDFLoader` for the
same behavior in #12092
- The `PyMuPDFLoader` changes required additional work in updating
`langchain.document_loaders.parsers.pdf.PyMuPDFParser` to be able to
process either an `io.BufferedReader` (from local pdf) or `io.BytesIO`
(from online pdf)
- The `PDFMinerPDFasHTMLLoader` change used a simpler approach since the
metadata is assigned by the loader and not the parser
  - **Issue:** Fixes #7034
  - **Dependencies:** None


```python
# PyPDFium2Loader example:
# old behavior
>>> from langchain.document_loaders import PyPDFium2Loader
>>> loader = PyPDFium2Loader('https://arxiv.org/pdf/1706.03762.pdf')
>>> docs = loader.load()
>>> docs[0].metadata
{'source': '/var/folders/7z/d5dt407n673drh1f5cm8spj40000gn/T/tmpm5oqa92f/tmp.pdf', 'page': 0}

# new behavior
>>> from langchain.document_loaders import PyPDFium2Loader
>>> loader = PyPDFium2Loader('https://arxiv.org/pdf/1706.03762.pdf')
>>> docs = loader.load()
>>> docs[0].metadata
{'source': 'https://arxiv.org/pdf/1706.03762.pdf', 'page': 0}
```

libs/langchain/langchain/document_loaders/parsers/pdf.py

@@ -235,7 +235,10 @@ class PyMuPDFParser(BaseBlobParser):
         import fitz
 
         with blob.as_bytes_io() as file_path:
-            doc = fitz.open(file_path)  # open document
+            if blob.data is None:
+                doc = fitz.open(file_path)
+            else:
+                doc = fitz.open(stream=file_path, filetype="pdf")
 
             yield from [
                 Document(

libs/langchain/langchain/document_loaders/pdf.py

@@ -194,7 +194,10 @@ class PyPDFium2Loader(BasePDFLoader):
         self,
     ) -> Iterator[Document]:
         """Lazy load given path as pages."""
-        blob = Blob.from_path(self.file_path)
+        if self.web_path:
+            blob = Blob.from_data(open(self.file_path, "rb").read(), path=self.web_path)
+        else:
+            blob = Blob.from_path(self.file_path)
         yield from self.parser.parse(blob)
 
 
@@ -284,7 +287,10 @@ class PDFMinerLoader(BasePDFLoader):
         self,
     ) -> Iterator[Document]:
         """Lazily load documents."""
-        blob = Blob.from_path(self.file_path)
+        if self.web_path:
+            blob = Blob.from_data(open(self.file_path, "rb").read(), path=self.web_path)
+        else:
+            blob = Blob.from_path(self.file_path)
         yield from self.parser.parse(blob)
 
 
@@ -318,7 +324,9 @@ class PDFMinerPDFasHTMLLoader(BasePDFLoader):
                 laparams=LAParams(),
                 output_type="html",
             )
-        metadata = {"source": self.file_path}
+        metadata = {
+            "source": self.file_path if self.web_path is None else self.web_path
+        }
         return [Document(page_content=output_string.getvalue(), metadata=metadata)]
 
 
@@ -357,7 +365,10 @@ class PyMuPDFLoader(BasePDFLoader):
         parser = PyMuPDFParser(
             text_kwargs=text_kwargs, extract_images=self.extract_images
         )
-        blob = Blob.from_path(self.file_path)
+        if self.web_path:
+            blob = Blob.from_data(open(self.file_path, "rb").read(), path=self.web_path)
+        else:
+            blob = Blob.from_path(self.file_path)
         return parser.parse(blob)
 
 
@@ -523,7 +534,10 @@ class PDFPlumberLoader(BasePDFLoader):
             dedupe=self.dedupe,
             extract_images=self.extract_images,
         )
-        blob = Blob.from_path(self.file_path)
+        if self.web_path:
+            blob = Blob.from_data(open(self.file_path, "rb").read(), path=self.web_path)
+        else:
+            blob = Blob.from_path(self.file_path)
         return parser.parse(blob)